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Biomedical subjects

M Huang

Publications and source records attributed to M Huang.

At least 307 records · Page 17Linked to original sources
PubMed1992

Susceptibility of inbred strains of mice to murine AIDS (MAIDS) correlates with target cell expansion and high expression of defective MAIDS virus.

Murine AIDS (MAIDS) is readily induced by the Duplan strain of defective murine leukemia virus in susceptible C57BL/6 mice. To identify mouse strains resistant to MAIDS, and to understand the genetic factors controlling susceptibility to the disease, we screened more than 20 inbred strains of mice for their susceptibility to MAIDS. For this study, mice of the Fv-1n/n, Fv-1b/b, or Fv-1n/b genotype were inoculated with stocks of defective MAIDS virus pseudotyped with N-tropic, B-tropic, or NB-tropic helper murine leukemia virus, respectively. Strains could be classified as susceptible, resistant, or moderately resistant. None of the individual H-2 haplotypes examined appears to explain resistance to MAIDS by itself. However, a very good correlation between the susceptibility or resistance phenotype and the presence or absence of defective proviral DNA and RNA in the spleen of these animals was found. Since the presence of defective proviral DNA and RNA reflects the oligoclonal proliferation of the cells infected by the defective MAIDS virus, our results strongly suggest that this target cell expansion is genetically controlled and is necessary and perhaps even sufficient for the development of the disease.

3T3 Cells↗
PubMed1992

Hemodynamic changes in rats after opening an arteriovenous fistula.

Time course of multiple hemodynamic changes in rats after opening an AV fistula was assessed. The fistula was made in male Sprague-Dawley rats by anastomosing the aorta and vena cava below the renal arteries. At 1 h (1H), 1 day (1D), 1 wk (1W) and 5 wk (5W) in sham controls or after opening an AV fistula, we measured cardiac output (CO) and tissue flows by using radioactive microspheres. The flow of microspheres to the lungs was used as a measure of shunt flow. In the fistula animals this lung flow (fistula flow) was 50-77% of the CO compared with 1-3% in the control animals. Cardiac index in the fistula animals increased by 40, 107, 129, and 307% compared with the respective control animals in the consecutive time groups. Systemic flow, tissue flows, and mean arterial blood pressure (MAP) in the fistula animals in the 1H and 1W groups were significantly decreased below control values, but each of these variables returned to control levels after 5W. Hematocrit (Hct) significantly decreased, whereas right atrial pressure (RAP) gradually increased over the experimental period. These two observations suggest retention of fluid. Plasma renin activity increased in the 1H animals but returned to control in the 1D animals. Atrial natriuretic peptide (ANP) gradually increased throughout the 5 wk from 86 +/- 22 (1H) to 709 +/- 217 pg/ml (5W). The increase in ANP correlated with the increase in RAP. Calculated total peripheral resistance in fistula animals was significantly decreased throughout the experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Hemodynamic studies in DOCA-salt hypertensive rats after opening of an arteriovenous fistula.

We determined the cardiovascular responses in normal and deoxycorticosterone acetate (DOCA)-salt hypertensive rats with reduced total peripheral resistance due to an arteriovenous (a-v) fistula. Animals were divided into four groups: control, fistula, DOCA-salt, and DOCA-salt fistula. The fistula was made by anastomosing the aorta and vena cava below the renal arteries. Four weeks after the creation of the fistula both DOCA-salt and DOCA-salt fistula animals received DOCA and salt for 6-8 wk. At the end of 10-12 wk we measured mean arterial pressure, cardiac output, tissue flows, and right atrial pressure. Flow measurements using radioactive microspheres were made in anesthetized animals. Cardiac index (CI) was 202% higher in the fistula group than in the control animals and 165% higher in the DOCA-salt fistula than in the DOCA-salt animals. There was no difference in cardiac output between the control and DOCA-salt animals. The increase in cardiac output was due to the fistula flow as evidenced by a significant increase in the number of microspheres in the lung. Mean arterial pressure was 115 +/- 4 mmHg (control) and 108 +/- 5 mmHg (fistula) in non-DOCA rats but increased in both DOCA groups, 159 +/- 3 mmHg (DOCA-salt) and 145 +/- 5 mmHg (DOCA-salt fistula). Right atrial pressure was increased above control in both fistula animals but was normal in DOCA-salt animals. Total peripheral resistance (TPR) was higher than control in DOCA-salt animals, but TPR in both the fistula and DOCA-salt fistula animals was lower than control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Development of hypertension in animals with reduced total peripheral resistance.

The object of the present study was to determine whether deoxycorticosterone acetate (DOCA)-salt hypertension can be produced in rats in the presence of low total peripheral resistance (TPR) induced by long-term administration of minoxidil, a vasodilator. The rats were divided into four groups: sham-control, DOCA-salt, minoxidil, and DOCA-salt with minoxidil. The rats in both DOCA groups had DOCA pellets implanted subcutaneously and were given saline to drink. The rats in both minoxidil groups were given minoxidil (3 mg/day) in the drinking water throughout the experiment. Final measurements, including mean arterial blood pressure, cardiac index, and renal blood flow were made after 4-6 weeks. Flow measurements were made using radioactive microspheres. Cardiac index (ml.min-1.100 g-1) in sham-control rats averaged 18 +/- 2 and was higher in the other groups: 23 +/- 4 (DOCA-salt), 25 +/- 2 (minoxidil), and 30 +/- 2 (DOCA-salt plus minoxidil). Mean arterial pressure (mm Hg) was increased in both DOCA-salt rats (160 +/- 8) and DOCA-salt plus minoxidil rats (153 +/- 5) as compared with sham-control (116 +/- 2) and minoxidil (113 +/- 3) rats. There was no significant difference in TPR between the sham-control and DOCA-salt rats, but TPR in minoxidil and DOCA-salt plus minoxidil rats was 30% and 28% lower than that in untreated sham-control and DOCA-salt hypertensive rats, respectively. In contrast, renal vascular resistance was significantly increased in both DOCA-salt groups as compared with non-DOCA-salt groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Study of cytogenetic damages in peripheral blood of styrene exposed workers].

The three indices of chromosome aberration (CA), sister-chromatid exchanges (SCEs) and micronuclei were used simultaneously to ascertain the cytogenetic effects on eighty-three styrene exposed workers under current industrial hygienic conditions in two glass fiber reinforced plastics factories. Our results showed that exposure to styrene at a concentration of 129.3 mg/m3 (range 48.3-223.9 mg/m3) could result in an increase of the frequencies of CA and micronuclei but had little influence on the frequency of SCEs.

Adolescent↗
PubMed1992

[The analgesic effect of red nucleus and preliminary research on its mechanism].

The spontaneous discharges of neurons in red nucleus (RN) of rats have been recorded with microelectrode. The discharge frequency of most RN neurons was changed by nociceptive electrical stimulation of nervi peronaeus communis or nervi tibialis or by nociceptive mechanical stimulation of tail or hind leg. The electrical activities of the somatic sensory neurons in the nucleus ventralis posterolateralis (VPL) of thalamus and of the visceral sensory neurons in the nucleus anterior and nucleus parafascicularis of thalamus have been recorded. According to the form of response to the peripheral nociceptive stimulation the neurons concerned could be divided into three types: pain-excited, pain-inhibited and pain-nonrelated. Electrical stimulating RN could change the spontaneous discharge frequency of somatic pain-related neurons of VPL and visceral pain-related neurons of nucleus anterior and nucleus parafascicularis, and could inhibit their response to somatic and visceral nociceptive stimulation respectively, but did not have influence on the activity of most pain-nonrelated neurons in VPL. The effects of electrical stimulating RN and microinjecting Ach into RN on the same pain-related neuron in VPL were similar. The experimental results show that RN can receive the somatic afferent impulses, that the excited RN can inhibit the transmission of somatic and visceral nociceptive impulses into the thalamus, and that the analgesic effect of RN is concerned with Ach.

Animals↗
PubMed1992

[Studies of plasmids of Pseudomonas maltophilia].

Eighteen strains of P. maltophilia were screened for the occurrence of plasmid using four different methods. Five of them were harbor plasmids. The results of plasmid detection in different growth phase of P2 strain showed that the highest amount of plasmids in the strain was observed in stationary growth phase. The characteristics of plasmid of P. maltophilia P2 was investigated by methods of agarose gel electrophoresis, restriction endonucleases analysis, determination of molecular weight. The results indicated that P. maltophilia P2 contained only one type of plasmid, its molecular weight was 4.4 x 10(6) dalton and that the plasmid had single BamHI. PstI. XbaI EcoRI. HindIII sites. Thus, the plasmid of P. maltophilia P2 may be developed into a fine cloning vector.

Molecular Weight↗
PubMed1992

[Inhibition of photosensitization of morin on DNA synthesis of ascites hepatoma cells].

Morin (0.012, 0.12, 1.2, 12.0 micrograms.ml-1) significantly inhibited the DNA synthesis of ascitic hepatoma (AH) cells. The inhibition of DNA synthesis and cell mortality was dependent on its concentrations as well as the illumination time. Photosensitization of morin was not due to 1O2 and O2-, but closely related to OH. and H2O2. The mechanism of the inhibition may be attributed to the damage of DNA replication template.

Animals↗
PubMed1991

Early dropouts from psychotherapy.

Ninety-six patients requesting psychotherapy were studied prospectively at the time of screening interview by four senior psychiatrists using a variation on Luborsky's Helping Alliance questionnaire and the Osgood Semantic Differential. Significant differences were found at the time of screening between early dropouts and continuers, among screeners' rate of early dropouts, and among patients' perceptions of screeners. The screener with a high early dropout rate was seen as being more passive and less potent, and offering less new understanding than other screeners. Patients who dropped out early experienced a less strong helping alliance, felt they gained less new understanding, liked the clinician less well, felt less well liked and less respected, and saw the interviewer as more passive and psychotherapy as less potent than did continuers.

Attitude to Health↗
PubMed1991

The majority of cells infected with the defective murine AIDS virus belong to the B-cell lineage.

Murine AIDS (MAIDS) is caused by a defective retrovirus which encodes a gag fusion protein (Pr60gag). We previously reported that this virus induced an oligoclonal proliferation of infected cells and suggested that this cell expansion was an important event in the pathogenesis of MAIDS. To identify these target cells, we constructed novel defective viruses whose genomes could be detected with specific probes. Helper-free stocks of these viruses induced MAIDS. Using in situ hybridization and immunocytochemistry and Southern analysis, we found that most infected cells belong to the B-cell lineage. Transformation of these B cells appears to be the primary event responsible for the development of immunodeficiency. This animal model may be relevant to our understanding of AIDS, of the immunodeficiencies associated with B-cell lymphoproliferative disorders, and of the role of B-cell proliferation and transformation in the effects of superantigens, since Pr60gag appears to be a superantigen.

Animals↗
PubMed1991

A generic intron increases gene expression in transgenic mice.

To investigate the role of splicing in the regulation of gene expression, we have generated transgenic mice carrying the human histone H4 promoter linked to the bacterial gene for chloramphenicol acetyltransferase (CAT), with or without a heterologous intron in the transcription unit. We found that CAT activity is 5- to 300-fold higher when the transgene incorporates a hybrid intron than with an analogous transgene precisely deleted for the intervening sequences. This hybrid intron, consisting of an adenovirus splice donor and an immunoglobulin G splice acceptor, stimulated expression in a broad range of tissues in the animal. Although the presence of the hybrid intron increased the frequency of transgenics with significant CAT activity, it did not affect the integration site-dependent variation commonly seen in transgene expression. To determine whether the enhancement is a general outcome of splicing or is dependent on the particular intron, we also produced equivalent transgenics carrying the widely used simian virus 40 small-t intron. We found that the hybrid intron is significantly more effective in elevating transgene expression. Our results suggest that inclusion of the generic intron in cDNA constructs may be valuable in achieving high levels of expression in transgenic mice.

Animals↗
PubMed1990

pH-dependent spectral and kinetic properties of cytochrome c peroxidase: comparison of freshly isolated and stored enzyme.

The effect of long-term storage on the electronic absorption spectrum and the kinetic properties of cytochrome c peroxidase has been investigated. No detectable differences were observed between freshly isolated enzyme and enzyme stored below -20 degrees C, in the crystalline state, for up to 41 months. The electronic absorption spectrum and the rate of the enzyme-hydrogen peroxide reaction are essentially independent of pH in 0.1 M potassium phosphate buffers for both fresh and stored enzyme. In buffers containing KNO3, the absorption spectrum and the kinetic properties of both fresh and stored enzyme vary with pH, consistent with the titration of an ionizable group with an apparent pKa of 5.5 +/- 0.1. The differences between phosphate- and nitrate-containing buffers are attributed to specific ion effects. In KNO3-containing buffers, the high-pH form of the enzyme reacts rapidly with hydrogen peroxide while the low-pH form is unreactive. Evidence is presented which indicates that both the low-pH and high-pH forms of the enzyme in KNO3-containing buffers are 5-coordinate, high-spin Fe(III) species.

Cytochrome-c Peroxidase↗
PubMed1990

Aldehyde dehydrogenase heterogeneity in rat hepatic cells.

In normal rat liver, aldehyde dehydrogenase (Aldehyde:NAD+ oxidoreductase, EC 1.2.1.3; ALDH) is found primarily in mitochondrial and microsomal fractions. During hepatocarcinogenesis, an additional tumor-associated aldehyde dehydrogenase (T-ALDH) is detectable in the cytosol of preneoplastic and neoplastic cells. We report here differences in the ALDH distribution pattern in different rat hepatoma cell lines compared to normal rat hepatocytes. Of the four basal ALDH enzymes, one mitochondrial ALDH and one microsomal ALDH account for 96% of total ALDH molecules detectable with our probes in normal hepatocytes. The other two mitochondrial and microsomal ALDH enzymes are only detectable in the appropriate subcellular fraction from large populations of cells. The tumor-associated ALDH is not detectable in normal hepatocytes. In addition to varying amounts of T-ALDH in the six different rat hepatoma cell lines examined, differences in the amounts of mitochondrial and microsomal ALDHs also occur in both high and low T-ALDH activity hepatoma cell lines. Each of five ALDH enzymes examined has a characteristic half-life varying from 45 min to 95 h.

Aldehyde Dehydrogenase↗
PubMed1990

Effects of hepatocarcinogenic initiators on aldehyde dehydrogenase gene expression in cultured rat hepatic cells.

The effects of certain in vivo inducers of tumor-associated aldehyde dehydrogenase (aldehyde:NAD+ oxidoreductase, EC 1.2.1.3; ALDH) activity on the expression of tumor-associated ALDH (T-ALDH) in vitro have been investigated using cultured rat hepatocytes and hepatoma cell lines. Two distinct groups of T-ALDH inducers have been identified. Three hepatocarcinogenic initiators 2-acetylaminofluorene, diethylnitrosamine and ethionine, which cause changes in T-ALDH in vivo, do not induce T-ALDH activity in cultured rat hepatocytes or hepatoma cell lines following either short-term or long-term exposures. In contrast, polycyclic aromatic hydrocarbons, such as 3-methylcholanthrene, benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene, induce an immediate increase of T-ALDH activity in both cultured rat hepatocytes and hepatoma cell lines. Synthesis and degradation rates of T-ALDH mRNA and protein have also been determined. The synthesis of T-ALDH protein is coupled with the increased synthesis of T-ALDH mRNA when the T-ALDH gene is constitutively expressed or activated by an inducer. Both T-ALDH mRNA (t1/2 = 25 - 34 h) and protein (t1/2 = 88 - 95 h) in high T-ALDH activity cell lines or low-activity cell lines treated with an inducer are relatively stable. Combined with previous studies, the results suggest that at least two different mechanisms are involved in T-ALDH gene expression; events occurring during initiation as well as during promotion appear to be involved in the genetically stable changes in T-ALDH gene expression which occur in vivo. The results also indicate that the lack of T-ALDH activity in normal hepatocytes or low-activity hepatoma cell lines is due to repression of the T-ALDH gene rather than to the differential stability of T-ALDH mRNA or protein.

2-Acetylaminofluorene↗